A: C++, unlike only about every other language with exceptions, is extremely accomodating while it comes to what you can throw. Actually, you can throw anything you akin to. That begs the question then, what should you throw?

In general, it's best to throw objects, not built-ins. If achievable, you must throw instances of classes which derive (ultimately) from the std::exception class. Through making your exception class inherit (ultimately) from the standard exception base-class, you are making life simpler for users (they have the alternative of catching most things by std::exception), plus probably you are providing them with more information (as the fact that your particular exception might be a refinement of std::runtime_error or whatever).

The common practice is to throw temporary:

#include

class MyException : public std::runtime_error {

public:

MyException() : std::runtime_error("MyException") { }

};

void f()

{

// ...

throw MyException();

}

Here, a temporary of type MyException is created & thrown. Class MyException inherits from class std::runtime_error that (ultimately) inherits from class std::exception.